1. Field Of The Invention
The present invention relates to top drive drilling units and particularly, a torque system for transmitting torque to break-out the upper pipe joint in the drill string from the top drive drilling unit.
2. Description of the Related Art
In the past decade, top drive drilling units have begun replacing the conventional rotary drilling units in the drilling industry. In a top drive drilling unit, the usual rotary table, kelly, and related equipment are substituted with an assembly which is connected to the upper end of the drill string which moves upwardly and downwardly in the derrick with the drill string. A drilling motor is connected to the drill string by a cylindrical stem and saver sub assembly extending downwardly from the drilling motor.
Drilling is accomplished by the powered rotation of the drill string. The drill string consists of threadably connected joints of drill pipe which are each about thirty feet long. Each end of each joint is threaded. One end has threads cut inside, and the other end is threaded on the outside. The inside threaded end is referred to as the "box," and the outside threaded end is the "pin." The threaded ends on the pipe joint are called tool joints. Tool joints are usually welded onto the ends of the tubular drill pipe body. When a drill string is made up, i.e., a series of pipe joints threadably connected, the pin is stabbed into the box and the connection tightened.
During the drilling operation, it may become necessary or desirable to disconnect or break-out the top drive drilling unit from the drill string at a point at which the threaded connection between the top drive drilling unit and the drill string are high above the drill floor of the drilling rig. The normal tools to disconnect the tightly threaded connection are heavy and large such that it is impractical to use them at any location other than the drill floor. Furthermore, it would be extremely dangerous for a worker to attempt to climb up the derrick and apply tools and the necessary torque to disconnect the joint.
It is desirable to be able to remotely disconnect the top drive drilling unit from the drill string at any height above the drill floor of the drilling rig. It is further desirable to have an apparatus which is quick and reliable and can be integrated into the top drive drilling unit to apply the required torque.